I'm researching down underquilts and I wanted opinions on the importance of a differential cut. I understand that its supposed to help prevent the compression of the down. In practice, does it really make that much of a difference? Would I have problems with an underquilt that didn't have a differential cut?

Hey Jeff, It depends on the quilt a little, the hanger some and the angle of the dangle….as it were. For a Down quilt though I would say it's pretty critical as it is so easily compressed with just a little tension off on the way the quilt is hung to the hammock. The down UQ's that we make are dual differential, so that the outside piece of fabric is larger both in length and width than the inner so that no matter how it is hung you can't compress the down. As the user of the hammock shifts and moves so that the quilt is pulled at varying angles the potential for down compression changes from side to side and end to end on a quilt. One that is not differential could make these areas compress, that is why we do dual differential on our underquilts.

another thing to consider is the baffle direction. like Paul's and my quilts, the baffles run vertically so you arent trying to force a flat piece of mesh to curve around the user, unnaturally.

personally, i tweaked my UQ to fit for the curve under the butt. at that area, most users will have a slight 3-5 degree curve from the torso and the legs. the dual differential at this point makes the quilt adapt to this curve without compression.

my summer version has only a one-way differential but it is sewn thru, so dual diff. would be impossible. still, i have taken the Breeze down to 31 degrees (to my own surprise)

Te-Wa makes a good point, there are differential quilts out there that would work perfectly–and there are pictures to prove it–if the user of the quilt is built like a sheet of plywood, totally flat. With the baffles running in line with the user the quilt is able to form around the shape of a loaded hammock much better.

I have a few full sized down underquilts(that I love) but my favorite is the one made by speer hammocks called the snug fit.It is cut with the dual differential baffles and really fits nicely under the hammock and eliminates any dead airspace or air gaps under the hammock.

Differential cut normally refers to the sizing of the outer sheeting being larger than the inner sheeting… This is important in under quilts designed to go below 30*… But more important is the use of body contouring radial shaped baffles to insure that full loft is maintained in use by under quilts designed for cold weather…Example the JRB Mt Washington 4 UQ, the original zero degree UQ… http://www.jacksrbetter.com/Mt%20Washington.htm.

The Speer Snug-fit, no longer in production, is another rare example that actually incorporates shaped baffles with differential design.